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Real-time applications such as video and voice services are a major driver for carrier Ethernet and are particularly susceptible to the effects of frame delay and loss. As a result, carrier Ethernet networks require advanced performance monitoring to enforce customer SLAs. This functionality is introduced by the international Telecommunication Union ITU-T Y.1731 which complements IEEE 802.1ag using manyu of the same functions and adding to them to deliver the following:
Frame Loss Measurement
Frame loss can be calculated by sending transmit and receive counters within CCMs for dual-ended measurements. The far end counters can then be compared with those produced locally to derive frame loss as a percentage
Frame Delay
Similarly, by using a timestamp in the DM (Delay Measurement), the receiving end can derive the time delay experienced across the network. This requires each service endpoint to have synchronized clocks. Alternatively DM message (DMM)/ DM replay (DMR) can be used to calculate the two-way frame delay; this method does not require clock synchronization.
Frame Delay Variation
Finally, ITU-T Y.1731 calculates frame delay variation (or jitter) by tracking frame DMs.
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